Telegraph system



A. D. DOWD.

TELEGRAPH SYSTEM.

APPLICATION FILED MAR. 29, 1918.

Patented Dec. 21,1920.

v3 as //1 V6/7 /0/ And/6W Q Dan d UNITED STATWEASBEENTI OFFICE.

ANDREW D. DOWD, OF I-IOIBOKEN, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW' YORK.

TELEGRAPH SYSTEM.

To all whom it may concern:

Be it known that I, ANDREW D. Down,-

The principal objects of this invention are to provide improved means whereby a receiving operator, who may be receiving a message, may interrupt the transmitting mechanism and signztl the operator at the transmitting station and also to provide improved means for maintaining the line cir- I cuit closed.

Other objects of this invention are to' provide a system of communication between any number of stations, which is flexible, one which requires a minimum amount of line time for the transmission of each character combination, and one which may readily be applied to existing circuits and be suitable for all classes of service.

A. further object is the provision of means whereby two or more current distributers located at different stations may be caused to operate in unison or to maintain proper phase relation without employing complicated and expensive speed correcting apparatus.

In handling telegraph communications, conditions sometimes arise which make it necessary for the operator at the receiving station to communicate with the operator at the sending station and it is often im perative that the receiving operator beable to interrupt the operation of thetransmitting apparatus and signal the transmitting operator promptly without Waiting for the transmitting operator to complete the sending of a message which may be'in process of transmission. In telegraph .work, such operations are known as breaking or operating break-in signals. For the accomplishment of the above object means is provided whereby a receiving operator may open the line circuit and through the in-,

strumentality of suitable electro-inechanism at the transmitting station arrest the transmitting distributing apparatus and operate a signaling device.

Specification of Letters Patent. Patented Dec, 21, 1920'.

Application fil ed March 29, 1918. Serial N0. 225,428.

Bymeans of this invention, any number of stations may be interconnected and any station may serve as a transmitting station, while any or all of the remaining stations may serve as receiving stations. The system of this inventionis herein described as arranged to work with a six-unit code and while suitable for use on all types of circuits, it is particularly intended for use on circuits of importance where line time is a controlling factor.

The invention contemplates the employment of current control means cooperating with a distributer to form units of current and no current for the line. The current control means may comprise a keyboard transmitter or an automatic tape transmitter, either of which may cooperate with the sending distributer to form characteristic groups of permutations. Associated with the sending distributer and controlled thereby is an electro-mechanism for automatically closing the line circuit. Means are also associated with thesending distributer which may be controlled by an operator at any receiving station for rendering the transmitting apparatus inoperative and operating a signaling device. A receiving distributer is also provided which operates in isochronism with the sending distributer and cooperates with an impulse responsive device to distribute the effects of the line current impulses to a suitable selecting mechanism. The latter distributer may be utilized when the line is not working duplex to distribute the effects of the outgoing line impulses to a home recording mechanism, thereby providing a home copy.

This system provides distributers with independent brushes for sending and receiving, each brush b'eing stopped automatically once per revolution, thereby insuring restoration to synchronism once per character. The system is especially adapted to operate on circuits including several stations and it permits greatervariation in the speed of the distributers than is allowed on multiplex circuits where a high degree of' unison is required between stations, consequently it is less diflicult and less expensive to maintain.

Theabove and other objects of this invention will be fully set forth inthe following description and claims and will be more readily understood by reference to the ac- .usu'al duplex balance.

companying drawing in which is disclosed diagrammatically one specific embodiment of the invention.

The system of this invention is here shown adapted for use with a six-unit code composed of units of current and no current, which is provided by simply opening and closing the line circuit as is done in Morse operation, but obviously other units, such as current impulse of different strength or different polarity, may be used without departing from the spirit of the invention. The system preferably employs a full metallic loop although a single line conductor with the usual ground return may be employed. V

The accompanying drawing discloses a transmitting and receiving arrangement such as may be employed at a single station. It is readily apparent that any number of stations similarly equipped may be connected in the loop in a similar manner and one station may be sending and all others receiving, or any two stations may transmit and receive simultaneously by providing the In the accompanying drawing A and B are two distributer faces, preferably parallel to each other, each face consisting of a plurality of segmented rings. The distributer arms 10 and 110 are frictionally mounted on a constantly rotating shaft 11, which may be driven by an suitable means, for example, amotor. ach distributer arm carries a pair of brushes which are adapted to sweep over the respective distributer faces and connect the segments of adjacent rings sequentially when the brush arm is released as will be hereinafter explained.

At 12 is represented a keyboard transmit ter which may be used for selectively actuating a plurality of current controlling contacts 15, 16,.17, 18 and 19, and a common keyboard contact 14. This mechanism may be of any suitable type, but prefer-ably of the typedisclosed in Patent No. 1,214,515, dated February 6, 1917. Applicants invention however, is not to be considered as limited to any particular type of transmitter, as an automatic tape transmitter may be employed.

A better understanding of the system can be obtained from a description of the selection of a particular character and the various operations which take place in transmit ting and recording the necessary impulses for the respective character. Let it be assumed, for example, that the character W is to be transmitted by the transmitter 12 and that the combination of signals required. is current, current, no current, no current, current. When the W. key of the keyboard (not shown) is depressed, the movable. contacts 15, 16 and.19 are moved into engagement and their respective stationary contacts and the common keyboard contact 14 are also closed (contact 14 being closed whenever any key-of the keyboard is depressed or whenever a new character combination is set up by the transmitter). The closing of these contacts completes energizing circuits through corresponding selecting relays 20, 21 and 24 respectively. These .circuits may be traced from grounded battery 13, upper windings of relays 20, 21 and 24, and contacts 15, 16 and 19 respectively in parallel, armature 40 and back contact thereof of lockout relay 25, contact and armature 32 of keyboard relay 35 and main transmitter contact 14 to ground. The selecting relays, by means of their upper ar matures, control contacts which may or may not be placed injseries with the line or loop, depending upon the selected or non-selected condition of the relays. Associated with the selecting relays is a distributer mechanism A for successively bringing into series relation with the line, the contacts which have been closed by the actuated relays. When the selecting relays are actuated, they also establish locking circuits for themselves from grounded battery 13, lower windings of the selectedrelays, lower armatures and contacts thereof, winding of keyboard relay 35, back contact and armature 41 of lockout relay 25 to ground.

A selection has now been set up and stored in,the group of selecting relays ready for distribution to the line. The selecting relays which have been actuated are now locked up over a circuit controlled exclusively by the armature of lockout relay 25 so that the energization at this time, of keyboard relay 35, while attracting armature 32 and thereby opening the energizing circuits of the selecting relays. does not destroy the selection set up. The attraction of armature 33 of keyboard relay 35 completes an energizing circuit for sending start relay 26 which may be traced from grounded battery '27, ring 28, brush 29, segment 30 of the sending distributer, front contact and armature 33 of keyboard relay 35, armature 31 and back contact thereof of break relay 34, and energizing winding of sending start relay 26 to ground. The energization of the sending start relay 26 causes the attraction of armature 36,'thereby closing an energizing circuit for sending start magnet 37. The magnet 37 upon being energized attracts its armature 38, thereby releasing the-distributer arm 10. passes off of segment 30, the start magnet 37 is deenergized and it's armature 38 falls back to engage the distributer arm upon the completion of each revolution. As illustrated in the drawing, all of the apparatus is shown in its unoperated position and by reason of the fact that sending start-control relay 45 is de'elnergized, the loop LL The instant the brush 29 100, by attracting its armature 101,'com

pletes a circuit from grounded battery 127, segment 128, brush 129, segment 130, energizing winding of receiving start magnet 137, armature 146 and back contact of receiving start-control relay 145, front contact and armature 101 of line relay 100 to ground. Receiving start magnet 137 thereupon attracts its armature 138 and permits the receiving distributer arm 110 to rotate in isochronism with the distributer brush arm 10. As soon as brush 129 passes off of segment 130, or as soon as the relay100 is deenergized, thereby opening the circuit of magnet 137, the armature 138 falls back 'in posltion to engage the distributer arm at the end of each revolution. Both distributer arms have now been released, and since they are adapted to travel at the same speed, the brush 39 of the sending distributer will connect segments 53, 54, 55, 56 and .57 with ring 50 at the same time brush 139 connects segments 153, 154, 155, 156 and 157 respec-' tively with ring 150.

When brush 39 engages segment, 53, the loop circuit is completed from line battery 40, contact and armature 58, of selecting relay 20, segment 53, brush 39, ring 50 to the other side of the loop. Completion of this circuit again causes the" energization of the line relays at the receiving stations, and since brush 139 is adapted to engage segment 153 while brush 39 is passing over segment 53, a circuit is com-plated from grounded battery 113, selecting magnet 120 of the selecting mechanism 112, segment 153,

brush 139, segment 150, front contact andarmature 101 of line relay 100 to ground. The selecting magnet 120 may rotate a disk or move a bar to perform some function in connection with the setting up of the mechanism for recording the character transmitted. When brush 39 engages segment 54, the loop circuit is completed through contact and armature 59 of selecting relay 21, and since brush 139 of thereceiving distributer is now in engagement with segment 154, a circuit is simultaneously completed through selecting magnet 121 of the selecting mechanism 112. The selecting relays 22 and 23 were not, actuated in set-- ting up the assumed combination, and consequently the loop will be open while the ing magnets 122 and 123, while brush 139,-

passes over segments 155' and 156 respectively.

Since wehave assumed the actuation of the selecting relay 24 in setting up the code combination for the character W, the loop should also be closed when the brush 39 engages segment 57. When the selecting relay 24 attracts its armature 62, a circuit is partially prepared from the grounded armature' 62, contact thereof, energizing winding of sending start control relay 45 to a local segment 61, which circuit will be'completed to grounded battery 27 when brush 29 connects rin 28 with segment 61. The energization o the sending start-control relay 45 causes the attraction of armature 46 and through the front contact thereof the loop circuit is completed When'the brush 39 engages segment 57, thereby closing the energizing circuit for the line relays and effecting'the actuation of the fifth selecting ma net 124 in a manner similar to the previous y mentioned selecting magnets. When relay 45 is energized. it establishes a holding cirlay 69 to ground. This locking circuit is broken when the brush 29 engages segment 78 and establishes an energizing circuit for relay 69. g

The sending starti-control relay 45 is controlled by the fifth si naling unit and is ac-- tuated, in case the fif th signaling unit consists of current, some time prior to the time of transmitting the fifth signalin unit to the line. The time of operation 0 relay 45 may be determined by the location of the local segment 61 on the distributer face. Immediately after the'distributer brush 39 haspassed over segment 56, the brush 29, engages a local segment 63 and completes a circuit from grounded battery 27, ring 28,

-. brush 29, segment 63, energizing WlIldlIlg possible in order to allow ample time to store 'up a new character combination on the selecting relays, while the preceding combination set up is being transmitted,

The receiving distributer brush 139, after passing off of the last of the receiving segments, engages a local segment 158 which may be used to complete a circuit through a printing magnet or any suitable recording device to record the character set up by the selecting mechanism.

As previously mentioned, this system is designed to operate on a six-unit code and the sending distributer is so constructed that the brush 39 when at rest interconnects the last signaling segment with ring 50. Therefore, it will be seen by reference to the accompanying drawing that the condition of the line or loop when messages are not being transmitted is dependent upon whether the last signaling unit of the last character transmitted consists of current or no current. If the last signaling unit consisted of ;current, the selecting relay 24 and the sending start-control relay, 45 would have been operated and the loop would be closed through armature 46 and front contact thereof of relay 45. However, if the last signaling unit consisted of no current, the loop would be open with the distributer at rest because the armature 46 of relay 45 would be out of engagement with its front contact and in engagement with its back contact which is connected to segment 52 of the "distributer. Thus, it will be seen that if the line is open while the brush 39 restson segment 57, it will be closed when the brush 39 engages segment 52, and vice versa. It is immaterial whether the line is open or closed when the brush 39 rests on segment 57 but it is important that the condition of the line when the brush 39 engages segment 52 be just the reverse of the line condition when the brush 39 rests on segment 57. As already explained, the system is designed to operate on the closed circuit Morse principle and if the line is open when the brush 39 interconnects the segment 57 with ring 50, the line should be closed when the brush 39 interconnects segment 53 with ring 50, that is, the condition of the line must be altered in order that the receiving distributer may be released to distribute the impulses transmitted fronrthe transmitting station.

Referring now to the apparatus at the receiving station, if the last signaling unit of a character combination consists of no current, the line will be opened and the line relay 100 will be deenergized so that the armature 101 will rest against its back contact. But since the line relay responds to each change in line condition and as a change in line condition always occurs when the transmitting distributer brush passes from the segment onwhich it normally rests onto the adjacent segment, the line relay 100 will respond and will attract its armature 101, thereby completing an energizing circuit for the receiving start magnet from grounded battery 127 segment 128, brush 129, segment 130, start magnet 137, armature 146 and back contact thereof of receiving start-control relay 145, armature 101 and front contact thereof to ground. Thus the receiving distributer arm 110 is released for rotation immediately after the transmitting brush arm 10 is released. On the other hand, if the last signaling unit of a character combination consists of current, then the loop will be closed when the sending distributer is at rest and the line relay armatures will be held in engagement with their front contacts. Also, in the latter event, the receiving start-control relay 145, the energizing circuit of which is in series with the last signaling segment and selecting magnet 124, will have been energized by the last signaling unit, and locked up over a circuit from grounded battery 160, armature 161 and back contact thereof of control relay 162, locking winding of relay 145, contact and armature 163 thereof to ground. Relay 145 when energized also attracts armature 146, thereby bringing the said armature into engagement with its front contact. Armatures 146 and 101 are now in engagement with their respective front con tacts and no circuit is established through the sending start magnet 137. However, the instant the sending brush 39 passes from segment 57 on to segment 52, the loop will be opened and the line relay armature 101 will fall back and engage its back contact, thereby completing a circuit through the receiving start magnet 137 from grounded battery 127, and as previously traced to armature 146 and front contact thereof, back contact and armature 101 to ground The control relay 162 is provided to control the locking circuit of the receiving start-control relay 145 and the former relay may be denergized immediately after the receiving distributer brush has been set in operation. This is accomplished when the brush 129 interconnects segment 184 with segment 128, thereby completing a. circuit through the control relay 162 from grounded battery 127. It will be noted that the receiving distributer may be set in opera- 'tion at will, and regardless of the character of the last signaling unit of any code combination.

Line circuit closing mechanism.

The system provides mechanism for closstated, the normal condition of the line 0 when an operator completes the transmission of a. message, is determined by the character ofgthe last signallng unit, unless the transmitting operator closes the loop or unless automatic line closing mechanism is provided for the purpose. If

the last unit of the last character transmitted consists of current, the loop will be closed through segment 57 and the front contact and armature 46 of relay 45. However, if the last signaling unit of the last character transmitted consists of no current, the loop will be open-at the front contact of armature 46 of relay 45. If the line circuit is left permanently open at any station, it is impossible for an operator at any other station connected on the line to transmit a message, because all stations are serially connected.

To overecome this feature, an electromechanism is associated with each transmitting distributer which will automatically close the line circuit in case it is left open upon the completion of the transmission of a message. A ratchet mechanism 64 is provided to close contacts 65, which mechanism is operated by a stepping magnet 66. Whenever the sending distributer is at rest and the loop is open, a circuit is completed from grounded battery 27, ring 28, brush 29, segment 30, stepping magnet 66, armature thereof and make-and-break contact 88 controlled thereby, back contact and armature 67 of relay 45, armature 68 and back contact thereof of release relay 69 to ground.

Attached to the armature 70 is a pawl 71 which is adapted to engage the ratchet 64 and step it ahead one step in the direction of the arrow upon each actuation of the magnet 66. A holding pawl 72 carried by armature 73 of release magnet 74 is provided to maintain the advance of the ratchet made by magnet 66. The circuit ofmagnet 66 is self-interrupted and this magnet will therefore continue to operate and step the ratchet 64 ahead until a member 75 carried thereby engages the flexible member 76 and closes contacts 65. The closure of contacts 65 establishes an energizing circuit for relay 45 from grounded battery 77, winding of relay 45, contacts 65 to ground. The energization of relay 45 performs several functions, first by the attraction of armature 67 it opens the energizing circuit of the stepping magnet 66 and closes a holding circuit for relay 45 from grounded battery 77, winding of relay 45, front contact and armature 67, armature 68 and back contact thereof of relay 69 to ground. Relay. 45 upon being energized also attracts armature 46, completing the line circuit through armature 46 and front contact thereof to segment 57 of the distributer, thereby placing the circuit in the same condition that it would have been in had the last signaling --impulse been a current impulse. Relay 45 when energized also attracts armature 83, but since the attraction of this armature performs no useful functionat this time its purpose will be described later. The holding circuit of relay 45 is maintained until brush 29 interconnects segment 78 with ring 28, thereby completing an energizing circuit for relay 69 as previously traced. Relay 69 upon being energized attracts its armature 68 and opens the holding circuit of relay 45 and also attracts its armature 75), thereby "completing an energizing circuit for release magnet 74 from grounded battery 89. Magnet 74, when energized, attracts its armature 73 and withdraws holding pawl -72 from engagement with the teeth of the ratchet 64, thereby permitting the ratchet to return to normal under the action of a suitable spring 80.

Break signal.

A novel arrangement is herein provided whereby an operator at any receiving station may instantly stop the sending distributer and cause the operation of a suitable signaling device at the sending station, which device will continue to operate until the sending operator responds to the call and opens the circuit of the signaling device. In accordance with this invention these features may be accomplished by any receiving operator by manipulating a key or switch 125 at the respective station to open the line circuit. The instant the line circuit is opened, armature 101 of the line relay 100 falls back and engages its back contact, and the instant brush 29 of the sending distributer engages segment 81 or 82, depending upon whether relay 45 is en ergized or denergized, a circuit will be completed through the break relay which may be traced from grounded battery 27,

' ring 28, brush 29, segment 81 or 82 and back contact and armature 83 or front contact and armature 83 respectively of relay 45, energizing winding of break relay 34, back contact and armature 101 of line relay 100 to ground. The energization of break relay 34 performs several functions. 'First, by the attraction of armature 31 the energizing circuit of sendingstart relay 26 is opened, thereby making it impossible for the start magnet 37 to be energized to release the distributer arm for further rotation and secondly, by the attraction of armature 84, a holding circuit is completed for the break relay and an energizing circuit for the signaling device, which may be traced from grounded battery 85, armature 84 and front contact thereof, locking winding of break relay 34, key 86 and contact thereof and signaling device 87 to ground. Thus it will be seen that once the break relay is operated it will remain locked up and the signaling device will continue to function until the sending operator responds to the call and opens the key 86. If desired, the core of relay 34 may be provided witli a copper sleeve to render it slow releasing and unresponsive to electrical changes in the holding circuit due to vibration of the signaling device 87.

The energizing winding of the break relay is provided with two branch circuits both of which are controlled by armature 83 of relay 45. The one branch circuit extends from the front contact of armature 83 to local segment 82 which is opposite segment 57 and the other branch circuit extends from the back contact of armature 83 to local segment 81 which is opposite segment 52. By means of this arrangement it is impossible for the signaling device to be operated by means of the line impulses because when a closed cricuit impulse is being transmitted, the energizing circuit of break relay 34 is open at the back contact of armature 101 of the line relay 100, and if an open circuit impulse is being transmitted while the brush 39 rests on segment 57 relay 45 will be de- 4 energized and the branch circuit to local segment 82 will be open at the front contact of armature 83. Again if an open circuit impulse is being transmitted while the brush 39 rests on segment 52, the previous impulse must have been a closed circuit impulse and accordingly the relay 45 would have been operated to close the front contact of armature 83 so that the branch circuit to segment 81 will be open at the back contact of arma ture 83. The signaling device 87 can be operated only when the line circuit is opened by means other than the transmitting means. This is one of the very. important features of this invention.

Various modifications may be made of the system herein disclosed without departing from the spirit of the invention.

What is claimed is:

1. In a telegraph system, a line circuit, a transmitting statlon and a receiving station, means to transmit groups of impulses of varying characteristics, means whereby one impulse of each grou may determine the character of an impu se of the succeedingv group, and a signaling device controlled by said last mentioned means and rendered operative by opening the line circuit.

2. In a telegraph system, means to transmit groups of impulses, a signaling device, means to set said signaling device in operation, a circuit for said means having two branches, and means to extend said circuit over one or the other of said branches de pending upon the character of the last transmitted impulse of a group.

3. In a telegraph system, a line circuit, means to transmit groups of impulses over said line circuit, a relay in said line circuit and responsive to all impulses transmitted, asignaling device, means controlled by said line relay to set said signaling device in 'means controlled by the last impulse of each group for determining the character ofthe first impulse of the succeeding group, a sigrraling device at one of said stations controlled by said last mentioned means, and means at another of said stations for effecting the operation of said signaling device.

5. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, means to transmit a starting impulse and a group of selecting impulses, means controlled by the last impulse of a group to determine the character of the starting impulse of the succeeding group, a signaling device adapted to be operated when the line circuit is opened, said signaling device being controlled by said last mentioned means.

6. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, means at the transmitting station to transmit successive groups of impulses in predetermined order, each group comprising a starting impulse followed by selecting impulses of various characteristics means, the action of which is determined by'the character of the last selecting impulse of a group to control the character of the starting impulse of the succeeding group, a signaling device associated therewith, and means at the receiving station for alterin the line condition to effect the operation of the signaling device.

7. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, means at the transmitting station to transmit successive groups of selecting impulses in predetermined order, means controlled by the last impulse of each group for determining the character of the first impulse of the succeeding group, a signaling device atsaid transmitting station, and means at the receiving station for altering the line condition to effect the operation of the signaling device.

8. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, means at the trans mitting station to transmit successive groups of impulses in predetermined order, means to render the first transmitted impulse of each group of a difl'erent character from that of the last impulse previously transmitted, a signaling device controlled thereby, and means at the receiving station for under the joint control of both said responsive means, a signaling device associated with the first mentioned responsive means, and means associated with the receiving apparatus for efiecting the operation of said signaling device While the transmitting dis-,

tributer is in operation.

10. In a telegraph system, a transmitting station and a receiving station, a line circuit, means at said transmitting station to transmit groups of selecting impulses, an intermittently operating distributer at the receiving station, means responsive to an impulse different in character from that of the last received impulse of a group to set said distributer in operation, means at the receiving station to open the line circuit, and

a signaling device at said first mentioned station unresponsive to the selecting impulses but responsive to the opening of said line circuit.

11. A telegraph system comprising a plurality of stations, a line circuit connecting said stations, a rotary distributer at each station, transmitting apparatus associated with the distributer at one station and receiving apparatus associated Withthe distributer at a second station, means for transmitting characteristic groups of current impulses from the transmitting station to the receiving station, a line' relay at the receiving station responsive to all of the line impulses, means at the, receiving station controlled by said line relay to set said distributer in operation, said means being respon-' sive only to a starting impulse when said impulse differs in clfaracter from that of the last selecting impulse of the preceding group, a signaling device also controlled by said line relay, and means for effecting the operation of said signaling device when the line circuit is opened at any receiving station. i

12. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, a rotary distributer at each of said stations, means to transmit groups of impulses of varying characteristics from the transmitting station to the receiving station, means whereby one impulse of each group may determine the character of an impulse of the succeeding group, and

means at the receiving station to stop the operation of the distributer at the transmitting station.

13; In a telegraph system, a transmitting station and a receiving station. a line circuit connecting said stations, a rotary distributer at each of said stations, means to transmit groups of impulses of varying characteristics from the transmitting station to the receiving station, means whereby one impulse of each group may determine the character of an impulse of the succeeding group, and means to open the line circuit to stop one of said distributers.

14. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, a rotary distributer at each of said stations, means to transmit groups of impulses of varying characterist'ics. from the transmitting station to the receiving station over the line circuit, means whereby one impulse of each group may determine the character of an impulse of the succeeding group, and means controlled from one station to stop the transmission of signals from the other station.

15. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, transmitting apparatus at one of said stations, receiving apparatus at another of said stations, means to transmit groups of selecting impulses from the transmitting station to the receiving station, means whereby one impulse of each group maydetermine the character of an impulse of the succeeding group, a signaling device associated with the transmit-.

ting apparatus, and means at the receiving station to stop the transmitting apparatus and operate the said signaling device.

16. In a telegraph system, a transmitting station and a receiving station, aline circuit connecting said stations, transmitting apparatus at one of said stations, receiving apparatus at another of said stations, means to transmit groups of selecting impulses from the transmitting station to the receiving station, means whereby one impulse of each group may determine the character of the impulse of the succeeding group, a signaling device associated with the transmitting apparatus, and means to open the line circuit to stop one of said distributersand operate said signaling device.

17. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, transmitting apparatus at one of said stations, receiving apparatus at another of said stations, means to transmit groups of selecting impulses from the transmitting station to the receiving station, means whereby one impulse of each group may determine the character of an impulse of the succeedin group, a signaling device associated with t e transmitting apparatus, and means at the receiving station to interrupt the operation of said transmitting apparatus and operate said signaling device.

18. In a telegraph system, a transmitting station and a receiving station, a line circuit connecting said stations, means to transmitsuccessive groups of signaling impulses in predetermined order, means controlled by the last impulse of each group for determining the character of the first impulse of the succeeding group, and an electro-mechanism for closing the line circuit When line impulses are not being transmitted, said electromechanism being under the control of the last mentioned means.

19. In a telegraph system, a transmitting station and a receiving station, an intermittently operating distributer at the transmitting station for transmitting groups of selecting impulses, a line circuit connecting said transmitting and receiving stations, the condition of the line circuit after the transmission of each group of signaling impulses being dependent upon the character of the last impulse transmitted, and a line circuit closing device controlled by the distributer for closing the line circuit When the distributer is at rest.

20. In a telegraph system, a plurality of telegraph stations, a line circuit connecting said stations, means to transmit successive groups of signaling impulses in predetermined order, means controlled by said transmitting means to determine the character of the first impulse of each successive group,

and a step-by-step line circuit closing device controlled by said last mentioned means for closing the line circuit when the transmitting means is at rest.

21. I11 a telegraph system, a transmitting station and a receiving station, a transmission line connecting said stations, an intermittently operable distributing mechanism for distributing current impulses to the line, and a device controlled by said distributing mechanism for automatically closing the line circuit When the distributer mechanism is at rest.

22. In a telegraph system, a transmitting station and a receiving station, a transmission line connecting said stations, an intermittently rotatable distributer for distributing current impulses to the line, and a device for automatically closing the linecircuit When the distributer mechanism is at rest.

28. In a telegraph system, a plurality of telegraph stations, a line circuit connecting said stations, means to transmit successive groups of signaling impulses in predetermined order, means controlled by the last impulse of each group for opening or closing the line circuit depending upon the character of said last impulse, and a step-by-step mechanism controlled by said last mentioned means for automatically closing the line circuit if left open a predetermined length of time.

In Witness whereof, I hereunto subscribe my name this 25th day of March, A. D., 1918.

ANDREW D. DOWD. 

